Tallinn University of Technology, the only technological university in Estonia, is the flagship of Estonian engineering and technology education. Here the synergy between different fields (technological, natural, exact, social and health sciences) is created and new ideas are born.

Story of the Song Arch you probably did not know before

There is probably no person in Estonia who does not know anything about the song festival. Nor anyone who has not heard about the Song Arch in Tallinn. However, the story of its creation is probably less known.

The singers’ voices have to reach far

The first song arch in Tallinn was completed as early as 1928. The song festival choirs sounded powerful there, but their voices would not reach the other side of the grounds. As the old song festival grounds were already worn out, in 1957, a competition was held for designing the new song arch. Architect Alar Kotli won the competition.

Kotli imagined the song arch as a bugle and made a cardboard model to depict that. In order to bring it into life, Heinrich Lauli, the best and well-known construction engineer of the day, had to be contacted.

Construction model tests produced one of Estonia’s most important projects

Heinrich Laul, Dean of the Department of Engineering at Tallinn Polytechnic Institute (now Tallinn University of Technology or TalTech), was one of the most outstanding Estonian engineers and building scientists of the 20th century. During his career, he took part in creating the Pärnu Beach Café, Hotel Palace, the grandstand building of the Kadriorg stadium among other things, and helped to restore the Estonia Theatre after the war.

Laul said that in order to achieve the character of a bugle, the song arch needs two arches: one in the back and one in the front. At the same time, it was important that the first arch would not have supports and would be ‘suspended in air’. If not, the singers would not be able to go under it.

People who have visited the song arch are now probably asking where the second arch is. Everyone knows the first arch, it is the one under which the singers sing. The second reinforced concrete arch leans on the columns of the back wall, and the first partly concrete-filled steel pipe hangs on cables between the first and second arch. Karl Õiger, Professor Emeritus of the School of Engineering at Tallinn University of Technology, believes that achieving this solution was complicated and unique, at least for that time.The durability of the structure was tested at the Polytechnic Institute under the guidance of Laul, where Õiger still studied at the time. Õiger explained that when developing different projects, they first created a model and then started testing it in the lab under load. After that, they would assess the environmental effects on the structure. Õiger remembers that Heinrich Laul used to say: ‘Model testing was actually designing the song arch.’

The strength of the Song Arch’s cables was higher than the factory expected

Karl Õiger has said that when the song arch was completed in 1960, the factory gave a 20-year guarantee for the cables. The whole weight of the roof is directed towards the front and back arches by 12 hollow suspension cables and stabilised by 19 additional curved cables. The diameter of the three-layered closed cables is 38.5 mm. In order to assess the state of the cables after exceeding the guarantee period by nearly three times, one suspension cable had to be removed and replaced with a new one, so that the old one could be examined from the inside.

Õiger remembers that five or six big building companies would not dare to take the risk – ‘What if it fails,’ they said. Luckily, one bridge building company was ready to risk it. Through lab tests, scientists concluded that the existing cables can surely be used for another 20–25 years. The wooden constructions of the song arch roof were completely replaced in the year 2019, the cables were cleaned and protected against corrosion.

Exegi monumentum!

There is probably no-one in Estonia who is not touched by the song festival and the Tallinn song arch. Karl Õiger is at a loss for words when he talks about the symbolic value of the song arch for Estonians. ‘During the Soviet times, that was the place one could go and speak their mind about how Estonian people felt about things. If normally we would have to sing about Lenin, then here, we would eventually sing the songs of Ernesaks,’ he says. ‘The song arch is a symbol that has to be preserved at all costs!’

Õiger motivates engineering students by saying that the results of their labour are visible for everyone and if they do a good job, their work will last decades or even hundreds of years. ‘I would recommend that young people follow the words of Horace: “Exegi monumentum!” – I built myself a monument.’

The article is based on the interview with Karl Õiger in the TV documentary With Wit and By Hand: A Hundred Years of Innovation (Mõistuse ja käega: 100 aastat innovatsiooni) and the book Tallinn University of Technology 1918–2018.